ACRO bug (fixed in 2.9.1b): while doing flips in ACRO mode, if you switch to Stabilize while inverted your throttle will go to minimum.  To regain throttle control you need to switch back to ACRO then back to Stabilize again (i.e. switch to stabilize twice).  You never lose control of roll/pitch/yaw.

Loiter/AltHold/Auto/RTL bug: if you switch into these modes with throttle at zero motors will go to minimum until you raise the throttle.

Auto mode altitude bug (fixed in 2.9.1b): setting a waypoint altitude greater than 320m over home altitude may wrap around and instead be interpreted as a low altitude.

ArduCopter 2.9 is now in the mission planner and the downloads area!

The major improvement is we use inertial navigation to improve altitude hold.  This increased reliance on the accelerometers means you must do some additional set-up before flying:

1. Perform the new accelerometer calibration in the mission planner (video).  The auto-trim metho has also changed (video).

2. Add vibration dampening foam between your frame and the APM.  Some suggested materials: DuBrogelhk foam.

 3. If upgrading from 2.8.1, modify the throttle and altitude PID values:

  • Increase your Throttle Rate P, reduce I to zero, increase D
  • Increase Altitude Hold P, reduce I to zero
  • Tune Throttle Accel P and I terms but try to keep P about 1/2 the size of I


Here is the list of major changes (a more detailed list can be found in the release notes):  

  • Alt hold using inertial navigation (Leonard, Randy, Jonathan)
    • AUTO_VELZ_MIN, AUTO_VELZ_MAX parameters control the max climb/descent rate for the autopilot (cm/s)
    • PILOT_VELZ_MAX controls max climb/descent rate for the pilot (in cm/s)
  • Landing improvements (Leonard/Randy).  Copter will descend to 10m or until an object is sensed with the sonar.  Then slows to 50cm/s descent (speed can be adjusted with LAND_SPEED parameter). (video).
  • Surface tracking with sonar (Randy/Leonard).  Copter will attempt to maintain current distance from objects in front of sonar regardless of altitude.  Only used in alt-hold and loiter, not used for missions.  Sonar can be enabled/disabled with CH7 switch. (video)
  • Failsafe improvements (Randy/Craig/John Arne Birkeland) including bug fixes, additional check for PPM encoder failure and implementation of battery failsafe.  Set-up instructions are here.
  • Mediatek gps driver accuracy improvements and use of SBAS [Craig].  Instructions on upgrading your mediatek to firmware 1.9 are here.
  • Traditional Heli improvements (Rob) including (a) bringing heli code back into the fold, (b) enabled rate controller (previously only used angle controllers). (c) fix to rotor speed controllers - now operates by switching off channel 8.  (d) allow wider collective pitch range in acro and alt hold modes vs stabilize mode  (e) bug fix to allow collective pitch to use the entire range of servos
  • Acro trainer (Leonard). Copter will return to be generally upright if you release the sticks in acro mode.
    • ACRO_TRAINER : set to 1 to enable the auto-bring-upright feature
    • ACRO_BAL_ROLL, ACRO_BAL_PITCH : controls rate at which roll returns to level
  • Camera control improvements (Randy/Sandro Benigno):  (a) AP_Relay enabled for APM2  (b) Trigger camera with CH7 or DO_DIGICAM_CONTROL command  (c) Allow pilot override of yaw during missions and fixed CONDITIONAL_YAW command.
  • PPM sum support for transmitters with as few as 5 channels (Randy/Tridge/John Arne Birkeland).
  • Performance and memory useage improvements (Tridge).


As per usual PIDs are optimised for the 3DR/jDrones quad with 850 motors and 10" props. If you're using more powerful motors/props and are seeing bad flight behaviour in stabilize, start by turning down Rate Roll P in 25% steps.

Special thanks to our testing team lead Marco and the dedicated bunch on the 2.8.1 release thread who put their copters at risk while testing the pre-release version.  Some of their videos are here: 1 2 3 4 5 6 7 8

Please feel free to report issues you find in the discussion below and/or add them to the issues list.


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Hello Eric,

CLI stands for Command Line Interface. It's built in Mission Planner in the Terminal TAB. You can learn how to use it here.

You have to enable raw logging in the Arducopter to see Accel Z (in CLI write logs <enter>, log raw <enter>, if may memory doesn't fail).

Anyway in CLI you can allways write help <enter> to see the commands that you can use (but please read first the link that I refer.

After flight you can download the logs and then examine the so much desired Accel Z :)



Oh, found it.

EV 15 means it "auto_armed" which means it's ready to do an auto function.  Not sure why that happened.  Then EV 29 is Reached_Alt.

I'm guessing you had a radio failure, it went to RTL, and immediately reached the target altitude, and then tried to land?  Not sure yet.

#define DATA_MAVLINK_INT32 2
#define DATA_MAVLINK_INT16 3
#define DATA_FAST_LOOP 5
#define DATA_MED_LOOP 6
#define DATA_AP_STATE 7
#define DATA_ARMED 10
#define DATA_DISARMED 11
#define DATA_AUTO_ARMED 15
#define DATA_TAKEOFF 16
#define DATA_LOST_GPS 19
#define DATA_BEGIN_FLIP 21
#define DATA_END_FLIP 22
#define DATA_EXIT_FLIP 23
#define DATA_SET_HOME 25

In mission planner, select terminal icon to open the Command Line Interface (CLI). This requires that you be connected using USB. The logs you want are on the flash memory on the APM and have to be downloaded to the computer to do the graphs. You can use the Log commands or use the Download Logs icon. Once downloaded, use the log browser to view them.

Brilliant jeff, I came very close to doing this myself, but then decided I just couldn't bring myself to strip all the DJI kit off the s8oo.


From experience with other big hexas, with low kv motors you should be good to go with rate_P at about 0.1 and stab)p at about 3.5. Keep rate_D at 0.003 or lower to begin with, the s800 vibrates like hell :)


Let us know how it goes!

I will let you know how it goes! I cannot justify the kind of money to upgrade my WKM to multi waypoint. But I have been searching and have not found any settings that have been done that I can trust. If you dump a DJI 450 its minor. Props on S800 are $35USD+ so I want to be extra careful. :)

Thank you. jeff

Thank you for pointing that out.

I really don't know how a failsafe could be triggered with the copter 1-2m away from me.

I never ever had a failsafe before and I find it very suspicious that other guys also do have failsafe issues now.

I had other issues with my Y6 with the APM2 with different rc versions of the 2.9.

Once the copter did a dive down to the ground in loiter. Could safe with a quick reflex.

The in loiter it suddenly flies away in one direction. I have this on video. I could take back controll by just using the right stick, but this was really scaring.

Take a look at this Video at around 1:30 I flew the copter in loiter mode. Then let go the stick at 1:36 and it stood still for a moment and then at 1:38 the copter wanted to fly away. Look at the speed.

A similar scare happened to me about a month ago with 2.81 on a hex. It was flying fair in loiter, seemed to want to search for the wrong heading. I switched to land in stabilize (I think), and for some reason I found it hard to set it down, then all of a sudden from about 1 foot off the ground and 10 feet away from me, it quickly started to climb and sped off to about 150 foot away, crashing into a tree about 25 foot high. My TX input made absolutely no difference, I had no control, it just took off rapidly. That particular flight I was not connected to MP, so I don't have any idea of what happened. I have made numerous flights since and no problem, but it is on my mind every time I fly now, very scary as it was about 10 feet away from me when it took off. Luckily it went off to my right, had it headed towards me, it would not have been pretty. I do not use fail safe, the only modes on my TX are stabilize, loiter and RTL. The only thing I could think of was that I may have moved the mode switch quickly from loiter (center position) to RTL (up) by mistake instead of to stabilize (down), however if that was the case I still should have had some control with my TX.
I was not using auto declinate, and was having some problems with my heading not being correct, that was the reason I wanted to land after a short flight. Not sure what the PROBLRM was.......Don

Today, I had nigh accident at altitude 100 meters by GPS lost about 2-3 sec but i change to ALT_hold and still under my control. I have video on my arducopter please look at 3.10 mins is begin have gps lost signal.


Interesting Balloons, I do not know if the code will automatically switch to alt-hold if it has a few satellites, I do not think it would be interesting however that he did to avoid this problem.

Yeah, not a S800, but I've flown it on a very powerful and heavy custom Octo, no issues.  Just need to tune it is all.

But, I don't understand about GPS lost signal or some other noise signal in my drone? 

Hello all and thanks for continuing the development of arducopter software.

Howewer I am experiencing a problem after the 2.9 upgrade.

When changing Stab_P to 0 for tuning.
After power cycling the APM it will load the default Stab_P = 4,5.

Have tried reflashed firmware on the APM 2.5, erased EEPROM but nothing.

Any thoughts on this ?

Best regards

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